This invention relates to a method of separating and taking out only the pulp from citrus fruits and also to an apparatus for practicing the same.
A conventional sequence of operations for pulp separation from citrus fruits, for example, from tangerines, is as follows.
Tangerines consist, as illustrated in FIG. 1, of an epicarp or peel a, an endocarp or segmental membrane b, and pulp d. The segmental membrane b and the pulp d combine to form segments c. The separation of the pulp d is accomplished by a series of operations as represented by a flow sheet in FIG. 2.
First, the tangerines ready for processing are led to a steaming step, in which they are passed through steam or hot water at about 90.degree. C. for two to three minutes to loosen the peel a from the underlying layer of the segmental membrane b, making the peel easier to separate. In a peeling step that follows, the fruits are moved through a peeler, where they are stripped of the peel a by a pair of pawled rolls. The peeled tangerines are divided, in a segmental step, into segments c, which usually number from 10 to 12 apiece. In a membrane-removal step the segments c are naked by a chemical treatment. The segmental membrane b is usually dissolved in an acid solution, followed by neutralization with an alkaline solution. The arrangements for this purpose comprise troughs in which the acid and alkaline solutions flows by gravity, so that the segments c flow concurrently with the solutions, in succession, for dissolution and removal of the segmental membrane b. Then, in a rinsing step, the pulp in the form of fully skinned segments c (hereinafter called "segmental pulp") is washed with water to remove the remnants of the chemicals. Like the arrangements used for the removal of the segmental membrane b, the device to be employed here is a trough, in which the segmental pulp flows together with water and are completely freed of the chemicals. In this way the segmental membrane b is removed and the pulp d consisting of the naked segments only, that is, segmental pulp, results. Ordinary canned tangerines are made by canning the pulp segments so obtained.
On the other hand, the pulp-sac-containing fruit drink of tangerines, so called because it is a mixture of tangerine juice with the juice vesicles, or sacs, of tangerine pulp, is usually prepared in the way now to be explained. The segmental pulp obtained in the manner above described is purchased from a tangerine canner and is subjected to a pulp-separating operation, in which the pulp segments are mixed with syrup and separated into the component juice vesicles or sacs. The sacs of pulp and syrup are blended with water and other additives to prepare the so-called pulp-sac-containing fruit drink.
As described above, the pulp of fruits, such as tangerines, for use in the pulp-sac-containing fruit drinks has heretofore been obtained by the ordinary method of producing the tangerine pulp for canning that involves a number of treatment steps. The arrangements used for those treatments, for example, the devices for removing the segmental membrane and rinsing the skinned fruits are made up of troughs hundreds of meters long for the flow of an acid or alkaline solution or water. Consequently, a large-scale plant and additional facilities for disposal of wastewater resulting from the use of acid and alkaline solutions are necessary. It is for this reason that juice manufacturers buy segmental pulp as their starting material from tangerine canners as above noted, and naturally the cost is high. In addition, the removal of the peel a in the afore-mentioned peeling step and the removal of the segmental membrane b in the membrane-removal step are not completely done mechanically, and it is common practice to complete it with human assistance. Among other problems of the conventional method is the deterioration in quality and taste of the tangerines due to the heat treatment by steaming.